fix errors in the POD, and test the POD

--- libdata-pageset-perl-1.05.orig/t/pod.t
+++ libdata-pageset-perl-1.05/t/pod.t
@@ -0,0 +1,6 @@
+use strict;
+use warnings;
+use Test::More;
+use Test::Pod;
+
+all_pod_files_ok();
--- libdata-pageset-perl-1.05.orig/lib/Data/Pageset.pm
+++ libdata-pageset-perl-1.05/lib/Data/Pageset.pm
@@ -109,7 +109,7 @@
 
 21
 
-=back 4
+=back
 
 =head3 Slide:
 
@@ -127,7 +127,7 @@
 
 24
 
-=back 4
+=back
 
 You can not change modes once the object is created.
 
